The present invention relates to a chemical deposition method, and more particularly, to a method of chemically depositing a film in which a catalyst component is employed to enhance the deposition rate.
As the overall dimensions of semiconductor devices continue to shrink, the demand is ever increasing to form a film of a uniform thickness despite the unevenness of substrate surface. For example, it should be accomplished in the manufacture of semiconductor devices to fill a contact hole with a diameter of about 100 nm and an aspect ratio of 10. Chemical deposition method has an advantage of forming a film of a relatively uniform thickness on an uneven substrate surface. However, this can be achieved only when the film formation is controlled by surface reactions. If the formation of a film is controlled by vapor phase reaction or mass transport rate at which the deposition sources travel to the substrate surface, although chemical deposition is utilized, it is difficult to obtain a film of uniform thickness. One solution to the above-mentioned problem is lowering the substrate temperature. Slow surface reaction, not the mass transport, controls the deposition rate and vapor phase reactions are suppressed at a lower temperature. However, the lowered surface reaction rate could increase the process time for forming a film of desired thickness.
In recent years, techniques of forming interconnects of semiconductor devices using copper have been brought to people""s attention. That is, copper would be a good substitute for a commonly-used aluminum because of increasing demands for high-speed semiconductor devices. The presence of copper will retard electromigration and improve the overall reliability of the interconnect structure. However, copper has disadvantages of difficult processing and low resistance to oxidation, compared with aluminum. For example, the etching process of a copper film requires much time because of the difficult processing. Consequently, damascene structures have been developed to simplify the process steps required to form electrical interconnect structures. Electroplating has been typically used to form a copper film, but chemical deposition or sputtering could preferably be used therefor considering the incorporation into other semiconductor processing.
The method of forming a copper film by chemical deposition is disclosed by Norman et al. in U.S. Pat. No. 5,085,731, U.S. Pat. No. 5,094,701, and U.S. Pat. No. 5,098,516. In the above patented techniques, a copper film was chemically deposited by using a volatile Cu+1-hexafluoroacetylacetonate-L complex as a deposition source, where L represents a neutral Lewis base. By using such a Cu+1 compound as a deposition source, a highly pure copper film could be obtained even at a substrate temperature of less than 200xc2x0 C. However, other articles report that the copper film deposited by such a method has a low deposition rate of 500 xc3x85/min and rough surface.
Accordingly, it is an object of the present invention to provide a method of chemically depositing a film at a higher deposition rate by providing high surface reaction rate without adversely affecting the step coverage.
In order to accomplish the aforementioned object, the present invention provides an improved method of chemically depositing a film by supplying gas phase sources on a substrate. The method comprises the step of introducing a catalyst component onto the substrate for facilitating the surface deposition reaction of the gas phase sources. The improvement is that the catalyst component is not buried under the film to be deposited but moved onto the surface of the film during the deposition. In the embodiments, the catalyst component can be introduced onto the substrate during or prior to the chemical deposition. Preferably, the film is a copper film and the catalyst component includes a halogen atom. More Preferably, the halogen atom is iodine or bromine.
In the case of using iodine catalyst component, the iodine is introduced by using a source selected from a group of consisting of iodine molecules, an alkane containing not more than 8 carbon atoms with iodine atoms substituted for hydrogen atoms up to four, a silicon-substituted alkane containing not more than 8 carbon atoms with iodine atoms substituted for hydrogen atoms up to four, the iodine-substituted alkane groups with fluorine or chlorine atoms substituted for at least one of remaining hydrogen atoms, and a molecule containing an iodine atom represented by the following formula (1).
R1Ixe2x80x83xe2x80x83(1)
wherein R1 represents hydrogen, alkylcarbonyl, carboxy, ether, or a substituted alkyl group with fluorines or chlorines substituted for hydrogens.
More particularly, the source for introducing the iodine can be selected from the group consisting of iodoethane, iodomethane, trifluoroiodomethane, diiodomethane, 2-iodopropane, and 2-methyl-2-iodopropane.
In the case of using bromine catalyst component, the bromine is introduced by using a source selected from a group of consisting of bromine molecules, an alkane group containing not more than 8 carbon atoms with bromine atoms substituted for hydrogen atoms up to four, a silicon-substituted alkane group containing not more than 8 carbon atoms with bromine atoms substituted for hydrogen atoms up to four, the bromine-substituted alkane groups with fluorine or chlorine atoms substituted for at least one of remaining hydrogen atoms, and a molecule containing a bromine atom represented by the following formula (2).
R2Brxe2x80x83xe2x80x83(2)
wherein R2 represents hydrogen, alkylcarbonyl, carboxy, ether, or a substituted alkyl group with fluorines or chlorines substituted for hydrogens.
More particularly, the source for introducing the bromine can be selected from the group consisting of bromotrimethylsilane, bromoethane, 2-bromopropane, and 2-methyl-2-bromopropane.
If a catalyst component such as iodine or bromine is introduced onto the substrate according to the above methods, a higher deposition rate can be achieved compared to the case of using the same deposition sources at a same temperature without the catalyst component.
The behavior of iodoethane on a copper single crystal is described by Lin et al. in Journal of Physical Chemistry, Vol. 96, p8529, 1992. In the article, the iodoethane is decomposed into iodine and an ethyl group on the (111) surface of copper single crystal at a relatively low temperature of less than 120 K. The decomposed ethyl group is desorbed as an ethene, leaving beta-hydrogen adsorbed on the copper surface at 274 K. The adsorbed hydrogen is desorbed as an ethane after being combined with an other ethyl group at 274 K, or desorbed as a hydrogen molecule at 320 K. As a result, iodine remains on the copper surface up to 950 K.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.